Silver halide photographic materials sensitized with a methine dye having an isoindolo(2,1 - a)benzimidazol -yl moiety

ABSTRACT

PHOTOGRAPHIC SILVER HALIDE EMULSIONS ARE PROVIDED WHICH CONTAIN A METHINE DYE HAVING AN ISOINDOLO(2,1-A) BENZIMIDAZOL-11-YL MOIETY.

United States Patent @fice Int. Cl. G03c 1/08 US. Cl. 96-129 14 ClaimsABSTRACT OF THE DISCLOSURE Photographic silver halide emulsions areprovided which contain a methine dye having an isoindolo[2,l-a]benzimidazol-l l-yl moiety.

This invention relates to novel photographic materials, and moreparticularly to new light-sensitive photographic silver halide emulsionscontaining certain methine dyes, and photographic elements preparedtherewith.

It is Well known to extend the spectral sensitivity of silver halideemulsions with various methine dyes. However, it has been found that notall methine dyes give satisfactory sensitizing results. Also, the numberthat can be used in practice is further limited by the Way in which thedye sensitizer performs when incorporated into silver halide emulsionlayers. For example, the clearness of the layers and the sharpness ofthe images produced therein, as Well as the keeping stability onstorage, particularly in regard to freedom from fogging and maintenanceof the desired level of selective sensitization, must not be adverselyafiected by the added dyes. For the purposes of color photography, it isrecognized as being especially important that the dyes used fully meetnot only the above requirements, but in addition, provide satisfactoryselective sensitivity in the emulsion layers. Relatively, few dyes areknown to meet such stringent requirements. Accordingly, it will beevident that there is need in the photographic art for new selectivelysensitized materials.

Accordingly, one object of this invention is to provide novelphotographic materials.

Another object of this invention is to provide lightsensitivephotographic silver halide emulsions containing certain methine dyes.

A further object of this invention is to provide novel photographicelements comprising a support material having thereon at least one layerof the above novel emulsions of the invention.

Other objects of this invention will be apparent from the followingdisclosure and the appended claims.

In accordance with one embodiment of this invention, photographic silverhalide emulsions are provided which contain a methine dye having anisoindolo[2,l-a]benzimidazol-ll-yl moiety.

We have now made the important discovery that methine dyes derived from5-substituted-1lH-isoindolo [2,1-a] benzimidazolium salts are especiallyuseful spectral sensitizers for light-sensitivity photographic silverhalide emulsions. These novel emulsions are characterized by having anextended sensitivity range of about from 5 80 to 700 nm., and evenhigher in some instances, with maximum sensitivity ranging from about550 to 650 nm. They are further characterized by good keeping qualitiesand causing relatively little, if any, fogging in. both fresh andincubated conditions. Also, the images produced therewith are ofexcellent quality, being clear, sharp and of good density.

In another embodiment of this invention, carbocyanine dyes are providedwhich comprise first and second nitro- 3,690,184 Patented Aug. 17, 1971gen containing heterocyclic nuclei joined together by a dimethine ortetramethine linkage; the first of said nuclei being anisoindolo[2,1-a]benzimidazole nucleus joined at the ll-carbon atomthereof to said linkage; and, said second nucleus being of the type usedin preparing cyanine dyes joined at a carbon atom thereof to saidlinkage, to complete said carbocyanine dye.

In still another embodiment of the invention, merocyanine dyes areprovided which comprise first and second nitrogen containingheterocyclic nuclei joined together by a methine or trimethine linkage;the first of said nuclei being an isoindolo[2,1-a]benzimidazole nucleusjoined at the ll-carbon atom thereof to said nucleus; and, said secondnucleus being a ketomethylene nucleus of the type used in merocyaninedyes joined at a carbon atom thereof to said linkage, to complete saidmerocyanine dye.

In still another embodiment of the invention, benzylidene dyes areprovided which comprise two nuclei joined together by a 'rnonomethine ora trimethine linkage; the first of said nuclei being anisoindolo[2,l-a]benzimidazole nucleus joined at the ll-carbon atomthereof to said linkage; and, said second nucleus being ap-dial'kylaminoaryl nucleus, joined at the 4-carbon atom thereof to saidlinkage, to complete said benzylidene dye.

Particularly useful methine dyes for practicing the invention includethose represented by one of the following formulas:

I Ru

e.g., fl-hydroxyethyl, w-hydroxybutyl, etc., an alkoxyalkyl group, e.g.,fl-methoxyethyl, w-butoxybutyl, etc., a carboxyalkyl group, e.g.,fl-carboxyethyl, w-carboxybutyl, etc., a sulfoalkyl group, e.g.,B-sulfoethyl, w-sulfobutyl, etc., a sulfatoalkyl group, e.g.,fi-sulfatoethyl, w-sulfatobutyl, etc., an acyloxyalkyl group, e.g.,fi-acetoxyethyl, 'y-acetoxypropyl, w-butyryloxybutyl, etc., analkoxycarbonylalkyl group, e.g., fi-methoxycarbonylethyl,w-ethoxycarbonylbutyl, etc., an aralkyl group, e.g., benzyl, phenethyl,etc., or an aryl group, e.g., phenyl, tolyl, naphthyl, methoxyphenyl,chlorophenyl, etc.; R represents an alkyl group (preferably a loweralkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl,isopropyl, butyl, hexyl, cyclohexyl, decyl, dodecyl, etc.; R representsan aryl group, e. phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl,etc.; R and R each represents a hydrogen atom, an alkyl group(preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g.,methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl,dodecyl, etc., an alkoxy group, e.g., methoxy, ethoxy, isopropoxy,butoxy, etc., a halogen atom, e.g., chlorine or bromine, and the like; Rand R each represents the same or different alkyl group (preferably alower alkyl containing from 1 to 4 carbon atoms) e.g., methyl, ethyl,propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl, dodecyl, etc.; Xrepresents an acid anion, e.g., chloride, bromide, iodide, thiocyanate,sulfamate, perchlorate, p-toluenesulfonate, methyl sulfate, ethylsulfate, etc.; Z represents the non-metallic atoms necessary to completea sensitizing heterocyclic nucleus of the type used in cyanine dyes,containing from 5 to 6 atoms in the heterocyclic ring, which may alsoinclude, in addition to the hetero nitrogen atom, a second hetero atomsuch as oxygen, sulfur, selenium or nitrogen, such as the followingnuclei:

a thiazole nucleus, e.g., thiazole, 4-methylthiazo1e, 4-phenylthiazole,S-methylthiazole, S-phenylthiazole, 4,5-dimethylthiazole,4,5-diphenylthiazole, 4-(2-thienyl)thiazole, benzothiazole,4-chlorobenzothiazole, S-chlorobenzothiazole, 6-chlorobenzothiazole,7-chlorobenzothiazole, 4-methylbenzothiazole, S-methylbenzothiazole,6-methylbenzothiazole, S-bromobenzothiazole, 6-bromobenzothiazole,4-phenylbenzothiazole, 4-methoXybenzothiazole, S-methoxybenzothiazole,6-methoxybenzothiazole, 5-iodobenzothiazole, 6-iodobenzothiazole, 4-ethoxybenzothiazole, S-ethoxybenzothiazole, tetrahydrobenzothiazole,5,6-dimethoxybenzothiazole, 5,6-dioxymethylenebenzothiazole,S-hydroxybenzothiazole, 6- hydroxybenzothiazole, naphtho[2,1-d]thiazole,naphtho [1,2-d]thiazole, fi,t-I-naphtho[2,3-d]thiazole,S-methoxynaphtho[2,3 d]thiazole, 5-ethoxynaphtho[1,2 d]thiazole,8-methoxynaphtho 2, l-d] thiazole, 7-methoxynaphtho [2, l-d] thiazole,4'-methoxythianaphtheno-7',6', 4,5-thiazole, etc.;

an oxazole nucleus, e.g., 4-methyloxazole, S-methyloxazole,4-phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethoxazole,5-phenyloxazole, benzoxazole, S-chlorobenzoxazole, S-methylbenzoxazole,5- phenylbenzoxazole, 6-methylbenzoxazole, 5,6-dimethylbenzoxazole,4,6-dimethylbenzoxazole, S-methoxybenzoxazole, S-ethoxybenzoxazole,S-chlorobenzoxazole, 6- methoxybenzoxazole, 5 -hydroxybenzoxazole,6-hydroxybenzoxazole, naphtho [2,1-d] oxazole, naphtho [1,2-d]oxazole,etc.;

a selenazole nucleus, e.g., 4-methylselenazole, 4-phenylselenazole,benzoselenazole, 5-chlorobenzoselenazole, S-methoxybenzoselenazole,5-hydroxybenzoselenazole, tetrahydrobenzoselenazole, naptho[2,1d]selenazole, naphtho[1,2-d]selenazole, etc.;

a thiazoline nucleus, e.g., thiazoline, 4-methylthiazoline,

etc.;

a pyridine nucleus, e.g., Z-pyridine, S-methyl-Z-pyridine,

4-pyridine, 3-methyl-4-pyridine, etc.;

a quinoline nucleus, e.g., Z-quinoline, 3-methyl-2-quinoline,5-ethyl-2-quinoline, 6-chloro-2-quinoline, S-chloro- Z-quinoline,6-methoxy-2-quinoline, 8-ethoxy-2-quinoline, 8-hydroxy-2-quinoline,4-quinoline, 6-methoxy-4- quinoline, 7-methyl-4-quinoline8-chloro-4-quinoline, l-isoquinoline, 3,4-dihydro-l-isoquinoline,3-isoquinoline, etc; and,

a 3,3-dialkylindolenine nucleus, e.g., 3,3-dimethylindolenine,3,3-dibutylindolenine, etc.; and

an imidazole nucleus e.g., imidazole, l-alkylimiclazole, l-

alkyl-4-phenylimidazole, 1-alky1-4,5-dimethylimidazole, benzimidazole,l-alkylbenzimidazole, 1-aryl-5,6-dichlorobenzimidazole, 1alkyl-lH-naphth[2,l-d]imidazole, 1-aryl-3H-naphth[1,2-d]imidazole,l-alkyl-S-methoxylH-naphth[2,l-d]imidazole, etc.; and the like;

and Q represents the nonmetallic atoms necessary to complete aheterocyclic nucleus such as the following nuclei:

a pyrazolinone nucleus (e.g., 3-methyl-l-phenyl-S-pyrazolinone,l-phenyl-S-pyrazolinone, 1-(2-benzothiazolyl)- 3-methyl-5-pyrazolinone,etc.),

an oxindole nucleus (e.g., 1-alkyl-2,3-dihydro-2-oxindoles,

etc.),

a rhodanine nucleus (i.e., 2-thio-2,4-thiazolidinedione series), such asrhodanine, 3-alkylrhodanine (e.g., 3- ethylrhodanine, 3ethoxycarbonyl-methylrhodanine, 3- allylrhodanine, etc.) or3-arylrhodanines (e.g., 3-phenylrhodanine, etc. etc.,

a 2-selena-2,4-thiazolidinedione nucleus (e.g., 3-ethyl-2-selena-2,4-thiazolidinedione, etc.),

a 2-thio-2,4-oxazolidinedione nucleus (i.e., those of the 2-thio-2,4(3H,5H)-oxazoledione series) (e.g., 3-ethyl-2-thio-2,4-oxazolidinedione, etc.),

a 2-thio-2,S-thiazolidinedione nucleus (i.e., the 2-thio-2,5(3H,4H)-thiazoledione series) (e.g., 3-ethyl-2-thio-2,5-thiazolidinedione, etc.),

a 2,4-thiazolidinedione nucleus (e.g., 2,4-thiazolidinedione,3-ethyl-2,4-thiazolidinedione, 3-phenyl-2,4-thiaz0lidinedione,3-a-naphthyl-2,4-thiazolidinedione, etc.),

a thiazolidinone nucleus (e.g., 4-thiazolidinone, 3-ethyl-4-thiazolidinone, 2 dicyanomethylene-3-ethyl-4-thiazolidinone,3-phenyl-4-thiazolidinone, 3-a-naphthy1-4-thiazolidinone, etc.),

a 4-thiazolin-one nucleus (e.g., Z-ethyl-mercapto-4-thiazolinone,2-alkylphenylamino-4-thiazolinones, 2-diphenylamino-4-thiazolinone,etc.)

a 2(3H)-thiophenone nucleus (e.g., 5-methyl-2(3H)-thiophenone, etc.),

a 2-imino-2,4-oxazolinone (i.e., pseudohydantoin) nucleus,

a 2,4-imidazolinedione (hydantoin) nucleus (e.g., 2,4- imidazolinedione,3-ethyl-2,4-imidazolinedione, 3-phenyl-2,4-imidazolinedione,3-a-naphthyl-2,4-imidazolinedione, 1,3-diethyl-2,4-imidazolinedione,1-ethyl-3-anaphthyl-2,4-imidazolinedione,1,3-diphenyl-2,4-imidazolinedione, etc.),

a 2-thio-2,4-imidazolinedione (i.e., 2-thiohydantoin) nucleus (e.g.,2-thio-2,4-imidazolinedione, 3-ethyl-2-thio- 2,4imidazolinedione,3-phenyl-2-thio-2,4-imidazolinedione,3-u-naphthy1-2*thio-2,4-imidazolinedione,1,3-diethyl-2-thio-2,4-imidazolinedione, 1-ethyl-3-phenyl-2- ethyl 2thio-2,4-imidazolinedione, 1-ethyl-3-phenyl-2-thio-2,4-imidazolinedione, 1-ethyl-3-a-naphthyl-2-thio-2,4-imidazolinedione, 1,3 diphenyl-2-thio-2,4-imidazolinedione, etc.),

a S-imidazolinone nucleus (e.g., 2-n-propylmercapto-5- imidazolinone,etc.), etc.

(especially a heterocyclic nucleus containing 5 or 6 atoms in theheterocyclic ring, 3 or 4 of said atoms being carbon atoms, 1 of saidatoms being a nitrogen atom, and 1 of said atoms being selected from thegroup consisting of a nitrogen atom, an oxygen atom and a sulfur atom).

The carbocyanine dyes defined by Formula I above are especially usefulspectral sensitizers for negative type silver halide emulsions, and arethe preferred class of sensitizers in this invention. They areconveniently prepared, for example, by heating a mixture of (1) anisoindolo[2,l-a]benzimidazolium salt of the formula:

wherein R R R and X are as previously defined, and (2) 'a heterocyclicsalt of the formula:

wherein m, L, R X and Z are as previously defined, and R represents ahydrogen atom or an acyl group, e.g., acetyl, propionyl, etc., inapproximately equimolar proportions, in the presence of a basiccondensing agent such as a trialkylamine, e.g., triethylamine, etc.,piperidine, N- methylpiperidineyetc, in ,a solvent medium such aspyridine, acetic anhydride, etc. The dyes are then separated from thereaction mixtures, and purified by one or more recrystallizations fromappropriate solvents such as ethanol, mixtures of ethanol anddimethylformamide, pyridine, and the like.

The merocyanine dyes defined by Formula II above are readily prepared byheating a mixture of (1) a compound selected from Formula IV above, and(2) a heterocyclic compound of the formula:

wherein d, L, R and Q are as previously defined, in approximatelyequimolar proportions, in the presence, of a basic condensing agent, andthe pure dye recovered in generally similar manner as described abovethe preparation of dyes of Formula I above.

The benzylidene dyes defined by Formula III above are advantageouslyprepared by heating a mixture of (1) a compound selected from Formula IVabove, and (2) a compound of the formula:

wherein g, R, and R are as previously defined, in approximatelyequimolar proportions, in the presence of a basic condensing agent,e.g., piperidine, in a solvent medium such as an alkanol, e.g., ethanol,etc. The purified dye is obtained by separation of the crude dye fromthe reaction mixture followed by one or more recrystallizations there offrom appropriate solvents such as methanol, mixtures of ethanol anddimethylformamide, and the like.

The intermediate isoindolo[2,1-a]benzimidazole (Bistrzycki and Schmutz,Ann. 415, 1 (1917)) with appropriate quaternizing agents, e.g., methyltosylate, ethyl tosylate, butyl tosylate, dimethyl sulfate, etc. Furtherdetails for their preparation can be had by reference to copendingappilcation of G. Irick, U.S. Ser. No. 642,238 filed May 29, 1967,wherein such intermediates are described and claimed, together with anumber of carbocyanine and benzylidene dyes prepared therewith, whichlatter are indicated as being useful for the specific purpose of dyeingfibers, yarns and fabrics.

In the preparation of negative silver halide photographic emulsions, thedyes of the invention are advantageously incorporated in the washed,finished silver halide emulsion and should, of course, be uniformlydistributed throughout the emulsion. The methods of incorporating dyesand other addenda in emulsions are relatively simple and well known tothose skilled in the art of emulsion making. For example, it isconvenient to add them from solutions in appropriate solvents, in whichcase the solvent selected should be complextely free from anydeleterious effect on the ultimate light-sensitive materials. Methanol,isopropanol, pyridine, water, etc., alone or in admixtures, have provensatisfactory as solvents for this purpose. The type of silver halideemulsions that can be sensitized with the dyes of the invention includeany of those prepared with hydrophilic colloids that are known to besatisfactory for dispersing silver halides, for example, emulsionscomprising natural materials such as gelatin, albumin, agaragar, gumarabic, alginic acid, etc. and hydrophilic synthetic resins such aspolyvinyl alcohol, polyvinyl pyrrolidone, cellulose ethers, partiallyhydrolyzed cellulose acetate, and the like.

The binding agents for the emulsion layer of the photographic elementcan also contain dispersed polymerized vinyl compounds. Such compoundsare disclosed, for example, in US. Pats. 3,142,568; 3,193,386; 3,062,674and 3,220,844 and include the water insoluble polymers of alkylacrylates and methacrylates, acrylic acid, sulfoalkyl acrylates ormethacrylates and the like.

The types of silver halide emulsions that can be sensitized with the newdyes of this invention include any of the conventional emulsionsprepared with light-sensitive silver salts including silver chloride,silver bromide, silver iodide, silver chlorobromide, silver bromoiodide,silver chlorobromoiodide, etc. The concentration of the new dyes in theemulsion can vary widely, e.g., from about 5 to about mg. per liter offlowable emulsion. The specific concentration will vary according to thetype of lightsensitive material in the emulsion and the effects desired.The suitable and most economical concentration for a given emulsion willbe apparent to those skilled in the art upon making the tests andobservations customarily used in the art of emulsion making.

To prepare a gelatin-silver halide emulsion sensitized with one of thedyes of this invention, the following procedure is satisfactory. Aquantity of the dye is dissolved in a suitable solvent and a volume ofthis solution containing from 5 to 100 mg. of dye is slowly added toabout one liter of a gelatin-silver halide emulsion. With most of thedyes, about from 5 to 20 mg. of dye per liter of emulsion suflices toproduce the maximum sensitizing effect with the ordinary gelatin-silverbromide (including bromoiodide and chlorobromide) emulsions. With finegrain emulsions, which include most of the ordinarily employedgelatin-silver chloride emulsions, somewhat larger concentrations of dyemay be necessary to obtain the optimum sensitizing effect. While thisprocedure has dealt with emulsions comprising gelatin, it will beunderstood that these remarks apply generally to any emulsions whereinpart or all of the gelatin is substituted by another suitablehydrophilic colloid, such as previously mentioned. It will also beunderstood that the above description is lntended to be illustrative andshould not be construed as limiting my invention in any sense since itis apparent that the new dyes can be incorporated by other methods 1nmany of the photographic silver halide emulsions and hydrophilic colloidlayers customarily employed in the art. For instance, the dyes can beincoporated by bathing a plate or film bearing an emulsion layer in asolution of one of the dyes in an appropriate solvent. Bathing methods,however, are not normally preferred.

The novel emulsions of this invention may be coated on any suitablephotographic support, such as glass, film base such as celluloseacetate, cellulose acetate butyrate, polyesters such as poly(ethyleneterephthalate), paper, baryta coated paper, polyolefin coated paper,e.g., polyethylene or polypropylene coated paper, which may be electronbombarded to promote emulsion adhesion, to produce the novelphotographic elements of the invention.

The following examples illustrate the preparation of a number ofspecific methine dyes that are useful for preparing the novel emulsionsand elements of the invention.

7 EXAMPLE 1 3',5-diethyl-1l-isoindolo[2,1-a]benzimidazolooxacarbocyanineiodide ethyl 11H isoindolo[2,1-a]benzimidazolium tosylate (1.22 g., 3mmol.), 2-acetanilidoviny1-3-ethylbenzoxazolium iodide (1.30 g., 3mmol.), triethylamine (0.6 ml.) and pyridine (7 ml.) are refluxed for 5minutes. The dye is precipitated by the addition of ether and the syrupyresidue washed with ether. It crystallized when stirred with ethanol.After chilling it is filtered off and dried. The yield is 0.59 g. (37%).After two recrystallizations from methanol, the pure dye melts at298-299 C.

dec.

EXAMPLE 2 3 ,5'-diethyl-ll-isoindolo[2,1-a1benzimidazolothiacarbocyanineiodide S =CHCH:

GEN r l (3 11 5 ethyl 11H isoindolo[2,l-a]benzimidazolium tosylate (1.22g., 3 mmol.), 2-acetanilidovinyl-3-ethylbenzothiazolium iodide (1.35 g.,3 mmol.), triethylamine (0.6 ml.) and pyridine (7 ml.) are refluxed for5 min. The dye is isolated as in Example 1. The yield is 1.41 g. (86%Twice recrystallized from methanol, the dye melts at 296-297 C., dec.

EXAMPLE 3 5'-ethy1-1,3,3-trimethylindo-11-isoindolo[2,1-a]benzimidazolocarbocyanine iodide H3 CCH;

GEN:

5 ethyl 11H isoindolo[2,1-a]benzimidazolium tosylate (1.22 g., 3 mmol.),2-acetanilidovinyl-1,3,3-trimethyl-3H-indolium iodide (1.34 g., 3mmol.), triethylamine (0.6 ml.), and pyridine (7 ml.) are refluxed for 5minutes. The dye is isolated as in Example 1. The yield is 0.94 g.(57%). After successive recrystallizations from methanol and ethanol,the dye melts at 301-302 C. dec.

:EXAMPLE 4 5,6-dichloro-1,3,5'-triethylbenzimidazolo-11'-isoindolo-[2,1-a]benzimidazolocarbocyanine iodide $2 5 Cl N Cl i J: CH CII= eEXAMPLE 5 3',5-diethyl-4,5-benzo-1l-isoindolo[2,1-a]benzimidazolothiacarbocyaninetosylate 5-ethyl-11H-isoindolo[2,l-a]benzimidazoliurn tosylate (1.63 g.,4 mmol.), 5-acetanilidomethylene-3-ethylrhodathiazolium tosylate (2.01g., 4 mmol.), acetic anhydride (0.6 ml.), triethylamine (1.1 ml.) andpyridine (10 ml.) are refluxed together for 8 minutes. The dye isisolated as in Example 1. The yield is 1.99 g. (77%). Twicerecrystallized from ethanol, the purified dye melts at 285- 286 C.

I 9 I? 2 5 I 02115 EXAMPLE 6 3-ethy1-5-[(S-ethylisoindole[2,1-a]benzimidazol-l 1- y1)methylene/rhodanine5-ethyl-11H-isoindolo[2,1-a]benzimidazolium tosylate (1.63 g., 4 mmol.),5-acetanilidomethylene-3-ethylrhodanine (1.22 g., 4 mmol.), aceticanhydride (0.4 ml.), triethylamine (1.1 ml.) and pyridine (10 ml.) arerefluxed together for 7 minutes and cooled. The dye is precipitated bythe addition of 10 ml. methanol, filtered 01f, and dried. The yield is0.53 g. (33%). After two recrystallizations from pyridine and one fromdimethylformamide, the pure dye melts at 275-276 C., dec.

EXAMPLE 7 1 1-p-dimethylaminobenzylidene-S-ethyl-11H- isoindolo[2,1-a]-benzimidazolium iodideS-ethyl-l1H-isoindolo[2,1-a]benzimidazolium tosylate (1.63 g., 4 mmol.),pdimethylaminobenzaldehyde (0.60 g., 4 mmol.), piperidine (6 drops) andethanol (10 ml.) are refluxed for 10 minutes and chilled. The dye isthrown out with ether. Because it is necessary to convert to the iodide,the precipitate is redissolved in ethanol (20 ml.) and precipitated by10 ml. of an aqueous solution of sodium iodide (0.60 g., 4 mmol.). Themixture is heated to boiling and chilled, and filtered. The dye isobtained EXAMPLE 8 11-p-dimethylaminocinnamylidine-S-ethyl-1lH-isoindolo I[2,1-a]benzimidazolium iodide 75,-ethy1-1lH-isoindolo[2,1-a1benzimidazolium tosylate (2.03 g., mmol.),p-dimethylaminocinnamaldehyde (0.92 g., 5.25 mmol.), piperidine (5drops), and ethanol ml.) are refluxed for 5 minutes. An ethanolicsolution of sodium iodide (0.75 g.) is added to precipitate the dye. Itis filtered off, washed with ethanol and Water, and dried.

The individual dyes dissolved in suitable solvents are The yield is 0.60g. (23%). Twice recrystallized from a mixture of dimethylformamide andethanol, it melts at 299-300 C.

The following example illustrates the preparation and the testing oflight-sensitive photographic silver halide emulsions and elements of theinvention containing therein the specific dyes of the preceding Examples1-8 as spectral sensitizers.

EXAMPLE 9 The individual dyes dissolved in suitable solvents are addedto separate portions of either a silver bromoiodide emulsion containing0.77 mole percent iodide or a silver chlorobromide emulsion containing40 mole percent bromide as indicated in Table 1 below, and at theindicated concentrations. After digestion at 52 C. for 10 minutes, theemulsions in each case are coated at a coverage of 432 mg. of silver persquare foot and 11190 mg. of gelatin per square foot on a celluloseacetate film sup port. A sample of each coating is exposed toa wedgespectrograph, and processed in Kodak D-19 developer which has thecomposition:

1 G. N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite (anhydrous) 90.0Hydroquinone 8.0 Sodium carbonate (monohydrate) 52.5 Potassium bromide5.0 Water to make 1.0 liter.

and then fixed, washed and dried. The sensitizing results are shown inthe following table.

TABLE 1.SENSITIZING DATA Dye concen- Emulsion tration, g./m. type silversensitizing maximum (nm.)

sensitizing range Dye of Example None No sensitization Control g1? 10these too will function in generally similar manner as useful spectralsensitizers for the preparation of other of the novel emulsions andelements of the invention.

Typical examples of such other dyes include, for example, 3,7-dichloro3',5 diphenyl-ll-isoindolo[2,1 a] benzimidazolo-oxacarbocyanine salt(e.g., the chloride, bromide, iodide, perchlorate, p toluenesulfonate,etc. salts); l',5-diethyl-3,7-dimethoxy 11 isoindolo[2,l-a]benzimidazolo-4-dicarbocyanine salt (e.g., the chloride, bromide,iodide, perchlorate, p toluenesulfonate, etc. salts)3,3,5,7,-tetraethyl-1 l-isoindolo [2,1-a]benzimidazoloselenacarbocyanine salt (e.g., the chloride, bromide,iodide, perchlorate, p-toluenesulfonate, etc. salts); l-phenyl-5- 5-phenylisoindol [2,1 a]benzirnidazol-11-yl)allylidene]-2-thiohydantoin;3-ethyl 5 [5,7-diethylisoindolo- [2,1a]-benzimidazol-llyl)allylidene]-2-thio-2,4-oxazolidinedione; .1l-p-dibutylaminobenzylidene-S -ethyl-i1lH-isoindolo[2,l-a]benzimidazolium salt (e.g., the chloride, bromide,iodide, perchlorate, p-toluenesulfonate, etc. salts); and the like.

Photographic silver halide emulsions containing the sensitizing dyes ofthis invention can also contain other addenda such as chemicalsensitizers, e.g., sulfur sensitizers (e.g., allyl thiocarbamide,thiourea, allylisothi cyanate, cystine, etc.), selenium and telluriumsensitizers. various gold compounds (e.g., potassium chloroaurate. aurictrichloride, etc.) (see US. patents to W.D. Baldsiefen, No. 2,540,085,issued Feb. 6, 1951; .R. E. Damschroder, No. 2,597,856, issued May 27,1952; and H. C. Yutzy et al., US. Patent No. 2,597,915, issued May 27,1952), various palladium compounds, such as palladium chloride (W. D.Baldsiefen, US. Patent No. 2,540,086, issued Feb. 6, 1951), potassiumchloropalladate (R. E. Staulfer et al., US. Patent No. 2,598,079, issuedMay 27, 1952), etc., or mixtures of such sensitizers; antifoggants suchas ammonium chloroplatinate (A. P. H. Trivelli et al., US. Pat. No.2,566,263, issued Aug. 28, 1951); benzotriazole, nitrobenzimidazole,S-nitroindazole, bermidine, mercaptans, etc. (see Mees, The Theory ofthe Photographic Process, MacMillan Pub., Revised Edition 1954, page677), or mixtures thereof.

The photographic silver halide emulsions and the other layers present inthe photographic elements made according to the invention can also behardened with any suitable hardener, including aldehyde hardeners suchas formaldehyde, and mucochloric acid, aziridine hardeners, hardenerswhich are derivatives of dioxane, oxypolysaccharides such as oxy starchor oxy plant gums,'and the like. The emulsion layers can also containadditional additives, particularly those known to be beneficial inphotographic emulsions, including, for example, lubricating materials,stabilizers, speed increasing materials, absorbing dyes, plasticizers,and the like. These photographic emulsions can also contain in somecases additional spectral sensitizing dyes. Furthermore, these emulsionscan contain color forming couplers or can be developed in solutionscontaining couplers or other color generating materials. Among theuseful color formers are the monomeric and polymeric color formers,e.g., pyrazolone color formers, as well as phenolic, heterocyclic andopen chain couplers having a reactive methylene group. The color formingcouplers can be incorporated into the photographic silver halideemulsion using any suitable technique, e.g., techniques of the typeshown in Jelley et al., US. Patent 2,322,027, issued June 15, 1943,Fierke et al., US. Patent 2,801,171, issued July 30, 1957, Fisher U.S.Patents 1,055,155 and 1,102,- 028, issued Mar. 4, 1913 and June 30,1914, respectively, and Wilmanns US. Patent 2,186,849, issued Jan. 9,1940. They can also be developed using incorporated developers such aspolyhydroxybenzenes, aminophenols, 3-pyrazolidomes, and the like.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof, it willbe understood that variations and modifications can be effected withinthe spirit and 1 1 scope of the invention as described hereinabove, andas defined in the appended claims.

We claim:

1. A photographic silver halide emulsion containing at least onecarbocyanine dye selected from those comprising first and secondnitrogen containing heterocyclic nuclei joined together by a linkageselected from the group consisting of a dimethine linkage and atetramethine linkage; the first of said nuclei being anisoindolo[2,l-a]benzimidazole nucleus joined at the 11-carbon atomthereof to said linkage; and said second nucleus being of the type usedin cyanine dyes employed in negative silver halide emulsions, saidnucleus being joined at a carbon atom thereof to said linkage, tocomplete said carbocyanine dye.

2. A photographic silver halide emulsion containing at least onemerocyanine dye selected from those comprising first and second nitrogencontaining heterocyclic nuclei joined together by a linkage selectedfrom the group consisting of a monomethine linkage and a trimethinelinkage; the first of said nuclei being an isoindolo[2,1-a]benzimidazolenucleus joined at the ll-carbon atom thereof to said nucleus; and saidsecond nucleus being a ketomethylene nucleus of the type used inmerocyanine dyes employed in negative silver halide emulsions, saidnucleus being joined at a carbon atom thereof to said linkage, tocomplete said merocyanine dye.

3. A photographic silver halide emulsion containing at least onebenzylidene dye selected from those comprising first and second nucleijoined together by a linkage selected from the group consisting of amonomethine linkage and a trimethine linkage; the first of said nucleibeing an isoindolo[2,1-a1benzimidazole nucleus joined at the 11- carbonatom thereof to said linkage; and said second nucleus being ap-dialkylaminoaryl nucleus joined at the 4- carbon atom thereof to saidlinkage, to complete said benzylidene cyanine dye.

4. A photographic silver halide emulsion containing at least one methinedye selected from those having one of the following formulas:

wherein n, m, d and g each represents a positive integer of from 1 to 2;L represents a methine linkage; R and R each represents a memberselected from the group consisting of an alkyl group and an aryl group;R and R each represents a member selected from the group consisting of ahydrogen atom, an alkyl group, an alkoxy group and a halogen atom; R andR each represents an alkyl group; Z represents the non-metallic atomsnecessary to complete a heterocyclic nucleus of the type used in cyaninedyes employed in negative silver halide emulsions, said nucleus havingfrom 5 to 6 atoms in the heterocyclic ring; and Q represents thenon-metallic atoms necessary to complete a heterocyclic nucleus of thetype used in merocyanine dyes employed in negative silver halideemulsions, said nucleus containing 5 atoms in the heterocyclic ring, 3of said atoms being carbon atoms, 1 of said atoms being a nitrogen atom,and 1 of said atoms being selected from the group consisting of anitrogen atom, an oxygen atom and a sulfur atom.

5. A photographic emulsion in accordance with claim 4 containing aphotographic color former.

6. A photographic silver halide emulsion containing at least onecarbocyanine dye selected from those represented by the formula:

wherein n and In each represents a positive integer of from 1 to 2; Lrepresents a methine linkage; R and R each represents a member selectedfrom the group consisting of an alkyl group and an aryl group; R and Reach represents a member selected from the group consisting of ahydrogen atom, an alkyl group, an alkoxy group and a halogen atom; Xrepresents an acid anion; and Z represents the non-metallic atomsnecessary to complete a heterocyclic nucleus of the type used in cyaninedyes employed in negative silver halide emulsions.

7. A photographic silver halide emulsion in accordance with claim 6 inwhich said 11 of said dye is 1 and said Z of said dye represents thenon-metallic atoms necessary to complete a heterocyclic nucleus selectedfrom the group consisting of a thiazole nucleus, an oxazole nucleus, atselenazole nucleus, a 3,3-dialkylindolenine nucleus and an imidazolenucleus.

8. A photographic silver halide emulsion containing at least onemerocyanine dye selected from those represented by the formula:

wherein said d represents a positive integer of from 1 to 2; Lrepresents a methine linkage; R represents a member selected from thegroup consisting of an alkyl group and an aryl group; R and R eachrepresents a member selected from the group consisting of a hydrogenatom, an alkyl group, an alkoxy group and a halogen atom; and Qrepresents the non-metallic atoms necessary to complete a. heterocyclicnucleus of the type used in merocyanine dyes employed in negative silverhalide emulsions,- said nucleus containing 5 or 6 atoms in theheterocyclic ring, 3 or 4 of said atoms being carbon atoms, I of saidatoms being a nitrogen atom, and 1 of said atoms being selected from thegroup consisting of a nitrogen atom, an oxygen atom and a sulfur atom. I

13 9. A photographic silver halide emulsion in accordance with claim 8in which said n of said dye is 1 and said Z of said dye represents thenon-metallic atoms necessary to complete a rhodanine nucleus.

10. A photographic silver halide emulsion containing at least onebenzylidene dye selected from those represented by the formula:

3',5-diethyl-1l-isoindolo[2,l-a]benzimidazolo-oxacarbocyanine iodide,

3,5-diethyl-1l-isoindolo[2,l-a]benzimidazolothiacarbocyanine iodide,

1 4 5'-ethyl-,3,3-trimethylindo-1 l-isoindolo[2,1-a]benzimidazolocarbocyanine iodide, 5 ,6-dichloro- 1,3,5-triethylbenzimidazolo-1 l-isoindolo- [2,1-a]benzimidazolocarbocyanineiodide,

3 ,5-diethyl-4',5-benzo-11-isoindolo[2,1-a]benzimidazolothiacarbocyaninetosylate,

3-ethyl-5-[(5-ethylisoindole[2,1-a]benzimidazolo-1l-yl)methylenehhodanine,

1 1-p-dimethylaminobenzylidene-S-ethyl-1 lH-isoindolo-[2,1-a1benzimidazolium iodide and 11-p-dimethylaminocinnamylidene-S-ethyl-1 lH-isoindolo-[2,1-a]benzimidazolium iodide.

12. A photographic element comprising a support having thereon at leastone layer containing a photographic silver halide emulsion of claim 1.

13. A photographic element comprising a support having thereon at leastone layer containing a photographic silver halide emulsion of claim 4.

14. A photographic element comprising a support having thereon at leastone layer containing a photographic silver halide emulsion of claim 11.

References Cited UNITED STATES PATENTS 3,243,298 3/1966 Libeer et a1.96105 J. TRAVIS BROWN, Primary Examiner US. Cl. X.R.

